The present invention relates to a diagnostic apparatus for a gas mixture supply apparatus and diagnostic method thereof. More particularly, it relates to a trouble diagnostic apparatus of the gas mixture supply apparatus of an internal combustion engine equipped with gas mixture supply means for supplying gas mixture from upstream of the main fuel injection valve, a diagnostic method thereof and improvement of fail-safe measures.
In the prior art proposal, fuel injected by a fuel injection valve is heated and evaporated by a heater provided on an intake passage, thereby reducing the amount of fuel deposited on the intake passage and intake valve, and improving combustion at the time of starting a freezer, in particular. It also proposes a method for reducing the emission volume of hazardous hydrocarbon. For example, U.S. Pat. No. 5,894,832 proposes that a fuel injection valve (upstream fuel injection valve) and a heater are installed in an auxiliary air passage for bypassing an upstream throttle valve in addition to a fuel injection valve main fuel injection valve) provided close to the intake port of each cylinder. This configuration allows fuel to be injected from the upstream fuel injection valve to the heater in the warm-up process after starting the freezer, and prevents fuel from depositing on the intake passage by fuel evaporation promoted by the heater, thereby improving combustion.
According to the aforementioned known example, furthermore, gas mixture formation is improved by supply of evaporated fuel into the cylinder, with the result that combustion is improved. Accordingly, stable combustion can be ensured even if the delay angle for ignition timing in the idling operation after startup is made greater than the conventional engine without heater. This provides an advantage of reducing the amount of emitted hazardous hydrocarbon (HC) after startup of the freezer, by heating and evaporating fuel through a heater and increasing the delay angle for ignition timing so that exhaust temperature is raised to promote the activity of catalyst. The aforementioned known example also discloses a method for evaluating an error by heater current value when the data current detecting means is provided.
Japanese Application Patent Laid-Open Publication Nos. 2000-213398 and 2000-274296 disclose a method for improving combustion in the area of high speed and high load especially through homogenous air intake in a direct injection spark ignition type internal combustion engine, alternating current they are not directly intended to improve of combustion at the time of freezer startup. Namely, they disclose a fuel injection control apparatus provided with switching control means to ensure that fuel supply function is shared between the main fuel injection valve for direction injection of fuel into a combustion chamber and an auxiliary fuel injection valve capable of supplying fuel in the intake passage, wherein they propose means for diagnosing a trouble of the auxiliary fuel injection valve based on a predetermined operation conditionxe2x80x94an air-fuel ratio detected in the area of high speed and high load, according to disclosed embodiments.
The prior art gas mixture supply apparatus, however, has the following problems.
According the aforementioned patent, when fuel is supplied from the upstream fuel injection valve, combustion is improved by allowing fuel to be deposited on the heater and to be evaporated therefrom. Accordingly, injection on the side of the main fuel injection valve is almost completely stopped during the use. Further, detection of heater current makes it possible to detect clearly a detectable phenomenon such as a heater current error, for example, when the heater has been extremely deteriorated or a cable of the power supply system for the heater has been disconnected. Even if there is an error as a gas mixture, however, an error of gas mixture cannot be detected when a not very conspicuous deterioration of heater performance has occurred or when an error of the upstream fuel injection valve has occurred even if there is no error as a heater performancexe2x80x94for example, when there is a decrease in the area pf flow path, hence decrease in the amount of fuel injection, for example, due to blocking of a passage for supplying fuel to the upstream fuel injection valve and mixture of foreign substances into the fuel injection valve or their deposition therein. Thus, supply of a sufficient amount of evaporation fuel is stopped without an error being identified as such, so the effect of combustion improvement cannot be ensured. This may lead to increase in the amount of emitted hydrocarbon, stalling of an engine or complete combustion failure in the worst case, according to the prior art.
In the operation mode where independent injection of a gas mixture supply apparatus with upstream fuel injection valve is performed after startup by the main fuel injection valve especially during the period of operation period including startup cranking, stalling of the engine occurs almost at the same time as it has started to rotate under its own power if there is an error in the gas mixture supply apparatus, for example, in the aforementioned heater or upstream fuel injection valve. Traveling cannot be performed in the worst case. Such a problem is found out in the prior art.
The art disclosed in Japanese Application Patent Laid-Open Publication Nos. 2000-213398 and 2000-274296 are intended to improve combustion in the area of high speed and high load especially though homogenous air intake in a direct injection spark ignition type internal combustion engine. So switch control means for sharing control with the main fuel injection valve by operating the auxiliary fuel injection valve is set in the area of high speed and high load, and setting is made in advance to ensure that the air-fuel ratio in concurrent use of the auxiliary fuel injection valve and main fuel injection valve denotes a rich mixture, while the air-fuel ratio when fuel is injected only from the main fuel injection valve shows a lean mixture. Accordingly, if air-fuel ratio in the case of the main fuel injection valve alone is set to a weakly lean level, there is no conspicuous change in combustion. So there is no deterioration in maneuverability which may be felt as a shock by an operator, and detection is possible in terms of changes of air-fuel ratio. From the viewpoint of the gas mixture supply apparatus alone, however, when an error has occurred to the gas mixture supply apparatus, deterioration in maneuverability is easily recognized. This requires deterioration of the state of combustion to be quickly detected. In the detection by an air-fuel ratio sensor, mainly the O2 concentration is detected, so output on the side of lean mixture may be produced even in the case of characteristic misfiring of the engine. Even if mixture is inadequate as a gas mixture, air-fuel ratio error is not detected when the ratio between air and fuel is not incorrect. Such a problem is found in the prior art. Further, the engine starts to rotate under its own power during the period of operation including startup cranking. This corresponds to the transient area characterized by a big change in combustion. Early detection of deterioration of the state of combustion is difficult, and diagnosis based on the air-fuel ratio may contain incorrect detection. Such problem is found out in the prior art.
The present invention has been made to solve the aforementioned problems. The object of the invention is to provide a diagnostic apparatus for gas mixture supply apparatus and diagnostic method thereof, capable of,
finding out an error in gas mixture by the gas mixture supply apparatus if there is any,
ensuring at least the engine startup,
permitting continued operation of the engine without a problem which may cause stalling of the engine, and
preventing deterioration of exhaust gas.
To achieve the above object, a diagnostic apparatus for the aforementioned gas mixture supply apparatus according to the present invention is basically characterized in that;
in a gas mixture supply apparatus of an internal combustion engine comprising,
a main fuel injection valve for supplying fuel to an internal combustion engine,
an upstream fuel injection valve for supplying fuel to the area upstream from the aforementioned main fuel injection valve, and
gas mixture supply means for supplying gas mixture from upstream of the aforementioned main fuel injection valve through an evaporation means for evaporating all or part of fuel supplied from the aforementioned upstream fuel injection valve;
the aforementioned diagnostic apparatus for the aforementioned gas mixture supply apparatus comprises,
gas mixture state detecting means for detecting the state of gas mixture when gas mixture is supplied from the aforementioned gas mixture supply means with the aforementioned evaporation means operating, and
evaluation means for evaluating an error of the aforementioned gas mixture supply means based on the result of detecting the aforementioned gas mixture state detecting means.
A diagnostic apparatus for the aforementioned gas mixture supply apparatus according to the present invention is basically characterized in that;
in a gas mixture supply apparatus of an internal combustion engine for supplying gas mixture from the area upstream of the aforementioned main fuel injection valve utilizing,
a main fuel injection valve for supplying fuel to an internal combustion engine, an upstream fuel injection valve for supplying fuel to the area upstream from the aforementioned main fuel injection valve, a heater member for heating all or part of fuel supplied from the aforementioned upstream fuel injection valve and evaporating it, and heater control means for controlling application of electric power to the aforementioned heater member;
the aforementioned diagnostic apparatus for a gas mixture supply apparatus comprising,
gas mixture state detecting means for detecting the state of gas mixture formed when fuel is supplied from the aforementioned upstream fuel injection valve with electric power applied to the aforementioned heater member by the aforementioned heater control means, and evaluation means for evaluating an error of the aforementioned upstream fuel injection valve and/or the aforementioned heater member based on the result of detecting the aforementioned gas mixture state detecting means.
The embodiment of a diagnostic apparatus for gas mixture supply apparatus according to the present invention is configured in such a way that; the aforementioned evaporation means consists of a heater member and heater control means,
the aforementioned gas mixture state detecting means detects gas mixture state based on the result of detecting one or more of the engine speed, intake manifold pressure, combustion pressure, torque value, exhaust temperature, HC concentration, NOx concentration and CO concentration, and evaluation means for evaluating the aforementioned error detests the state of gas mixture based on the result of detecting at least one of the aforementioned gas mixture state detecting means, the amount and rate of change, deviation from a predetermined target value and fluctuating surge.
A diagnostic apparatus for gas mixture supply apparatus according to the present invention configured in the aforementioned manner identifies an error if the state of gas mixture is detected and a predetermined preset degree of deterioration is exceeded, in cases where the gas mixture supply apparatus has (1) a heater-related error caused by  less than a greater than  decrease in the amount of evaporated fuel supplied from the upstream fuel injection valve due to heater deterioration and  less than b greater than  disconnection of a cable in power supply system for the heater; or (2) a gas mixture-related error caused by decrease in the area exposed to flow or decrease in the amount of fuel injection due to blocking of fuel supply passage leading to the upstream fuel injection valve or entry or deposition of foreign substances in the fuel injection valve.
A diagnostic apparatus for gas mixture supply apparatus according to the present invention further comprises fail-safe control means which immediately or progressively implements (1) a step of reducing the amount of fuel or stopping the supply of fuel in response to the evaluation made by the aforementioned evaluation means as containing an error, (2) a step of increasing the amount of fuel supplied from the aforementioned main fuel injection valve or switching to the aforementioned main fuel injection valve, (3) a step of stopping the aforementioned evaporation means or stopping application of electric power to the aforementioned heater member, and (4) a step of correcting ignition timing;
wherein the aforementioned fail-safe control means is used in such a way as to prevent the operation status of the aforementioned internal combustion engine and/or the amount of exhaust gas from being deteriorated.
A diagnostic apparatus for gas mixture supply apparatus according to the present invention configured in the aforementioned manner at least ensures engine startup, permits continued operation of the engine and prevents deterioration of exhaust gas.
A diagnostic apparatus for gas mixture supply apparatus according to the present invention further comprises;
main fuel supply evaluation means containing (a) a step of injecting fuel through the aforementioned main fuel injection valve at least during start cranking, and (b) a step of evaluating fuel supply as being normal through the aforementioned main injection valve when engine speed has exceeded a predetermined level or intake manifold pressure has been reduced below a predetermined level; and
a fuel supply change means containing (a) a step of reducing the amount of fuel or stopping the supply of fuel in response to the evaluation made by the aforementioned main fuel supply evaluation means as being normal, (b) a step of increasing the amount of fuel supplied from the aforementioned upstream fuel injection valve or switching to the aforementioned upstream fuel injection valve, and (c) a step of performing operation of the aforementioned evaporation means or applying electric power to the aforementioned heater member.
A diagnostic apparatus for gas mixture supply apparatus according to the present invention configured in the aforementioned manner is characterized in that, at least when the aforementioned main fuel supply means evaluation by a main fuel injection valve has been found out to be normal, diagnosis is performed by the upstream fuel injection valve selected by switching. This characteristic avoids incorrect evaluation which may be caused by evaluation of an error in gas mixture supply means being adversely affected by the error of the aforementioned main fuel supply means.
A diagnostic apparatus for gas mixture supply apparatus according to the present invention further comprises;
an auxiliary air passage for bypassing a throttle valve,
an auxiliary air passage valve for regulating the amount of air in the aforementioned auxiliary air passage,
target speed control means for controlling the aforementioned auxiliary air passage valve to reach a predetermined target speed after the aforementioned internal combustion engine has started and has been evaluated,
ignition timing control means for controlling ignition timing to be on the side of delay angle at least when fuel is supplied from the aforementioned upstream fuel injection valve, and
evaluation means for evaluating one or more errors in the aforementioned upstream fuel injection valve, heater member and auxiliary air passage valve, based on the result of detection by the aforementioned gas mixture state detecting means when the aforementioned ignition timing is controlled to be on the side of delay angle.
A diagnostic apparatus for gas mixture supply apparatus according to the present invention configured in the aforementioned manner is characterized in that the degree of deterioration can be evaluated while the state of combustion of ignition timing with respect to delay angle is detected. This avoids extreme increased in the amount of hydrocarbon emission or the worse stalling of an engine.
Another embodiment of the present invention is characterized in that the aforementioned ignition timing control means performs control of ignition timing in terms of delay angle in a predetermined number of times.
Still another embodiment of the present invention is characterized in that the aforementioned gas mixture state detecting means detects the state of gas mixture based on the result of detecting one or more of the amounts of air, auxiliary air passage valve control and fuel injection.
A further embodiment of the present invention is characterized comprising;
means for evaluating the deterioration of battery, and
means for evaluating the aforementioned gas mixture supply means for an error based on the result of detecting battery voltage when fuel is supplied from the aforementioned upstream fuel valve after evaluation is made to determine that a battery is not deteriorated.
Still further embodiment of the present invention is characterized in that the aforementioned gas mixture state detecting means detects the state of gas mixture based on;
the result of detection by heater current detecting means for detecting the current applied to the aforementioned heater member, and the aforementioned heater current detecting means subsequent to electric power to the aforementioned heater member having been applied to the aforementioned heater member; and the trouble setup value of a heater current to be set in conformity to the amount of fuel injection in advance.
Still further embodiment of the present invention is characterized by comprising error storage means for storing an error when such an error has been found out by the aforementioned evaluation means, and/or error alarm means for alarming an error.
Still further embodiment of the present invention is characterized in that the aforementioned evaporation means performs at least one of evaporation by an electric heater, heater evaporation by combustion, evaporation by ultrasonic vibration, evaporation by hot water and evaporation by exhaust gas temperature.
A diagnostic method for gas mixture supply apparatus according to the present invention is characterized by comprising;
a main fuel injection valve for supplying fuel to an internal combustion engine,
an upstream fuel injection valve for supplying fuel to the area upstream from the aforementioned main fuel injection valve, and
gas mixture supply means for supplying gas mixture from upstream of the aforementioned main fuel injection valve through an evaporation means for evaporating all or part of fuel supplied from the aforementioned upstream fuel injection valve; the aforementioned diagnostic method further comprising;
a step of detecting the state of gas mixture when gas mixture is supplied from the aforementioned gas mixture supply means with the aforementioned evaporation means operating, and
a step of evaluating an error of the aforementioned gas mixture supply means based on the aforementioned result of detection.